Abstract [en]

This thesis aims to assess the environmental consequences of management strategies for wood waste in Sweden. There is a special focus on separation strategies and in what way such measures influence environmental aspects such as the presence of heavy metals in the waste. Actors’ incentives and capacity to influence wood waste management are analysed, emphasising the importance of driving forces such as governmental regulation and market interactions.

The results show that, in comparison to present dilution practice, separation of contaminants would lead to decreased heavy metal emissions during combustion of wood waste while still recovering a similar energy yield from the waste. Such measures would also increase possibilities for resource-saving reuse of the generated ash. For most metals, however, long-term pollution concerns related to accumulations in landfills and unintentional co-recycling are difficult to address, regardless of separation strategy. An exception is industrial preservative-treated wood waste that according to regulation is to be separately handled as hazardous, for which separation measures also would address such future concerns. This indicates that governments could play an important role in environmental policy by, for instance, stimulating separate handling of certain discarded products.

Actors in the energy sector involved in fuel and heat production have quite restricted capacities for separation of contaminants in wood waste. Instead, achieving substantially less contaminated wood waste seems to require actors in the waste and construction sectors to develop source separation measures. The fact that such measures often involve actors lacking professional standards for waste management constitutes a fundamental obstacle to efficient separation. Perhaps even more hampering is that source separation at present leads to increased waste disposal costs for actors in the construction sector. Such economic outcomes of source separation are unfavourable, since these actors consider wood waste as a disposal problem for which the costs should be minimised. Despite these obstacles, however, the results show that some actors have proved capable of achieving relatively efficient separation.

At present, only a minor share of industrial preservative–treated wood waste is separately handled as hazardous. For actors in the energy, waste and construction sectors, the incentives for such measures appear low even though introduced regulations potentially could have created such incentives. It appears as if a lack of steering mechanisms such as communication and supervision have neutralised the inherent pressure from regulation in many cases. Quality requirements, on the other hand, can be concluded to be of outmost importance for motivating separation measures. Unfortunately, market forces encourage actors in the energy sector to practice inconsistent enforcement of quality requirements. As a consequence, actors in the waste and construction sectors do not experience any strong pressure for separation of contaminants from their customers. In fact, such an inconsistent enforcement of quality requirements seems to have counteracted legal pressures for separation, due to present customer-oriented business management.

Abstract [en]

Large amounts of recovered waste wood (RWW) originating from construction and demolition activities (C&DWW) and industrial activities (IWW) are annually generated in Sweden. RWW is also imported for use as an energy source at biofuel boilers. Increased use of biomass is one strategy to decrease environmental impact, in general, and the emissions of green house gases, in particular. This study addresses the environmental and resource implications of metal occurrence in RWW that is used as an energy source at biofuel boilers. RWW contains elevated concentrations of arsenic, chromium, copper, zinc, mercury, nickel, lead and possibly cadmium. The metal composition of Swedish and imported RWW differs in that Swedish RWW contains higher concentrations of arsenic, chromium, zinc, nickel and copper, while imported RWW contains higher concentrations of lead, mercury and cadmium. Ashes from combustion of RWW are nowadays generally disposed in landfills due to their elevated metal concentrations. This practice makes it impossible to use these ashes as filler material thereby replacing extraction of raw materials and decreasing the need for landfill space. Furthermore, landfilling leads to accumulation of hazardous heavy metals that poses a future environmental and health problem. If RWW from construction and demolition should contribute optimally to a sustainable energy system, cleaner waste wood flows are a prerequisite. The elementary measure is to track potential pollution sources in this waste stream and find out which are significant. Furthermore, since most of the RWW is untreated and unpolluted wood, there is a great environmental potential to separate this flow through the waste management system. Such an approach might lead to decreased environmental pollution of heavy metals and an improved resource management.

Abstract [en]

In this paper, wood waste (RWW) recovered for heat production in Sweden was studied. Previous research has concluded that RWW contains elevated amounts of heavy metals, causing environmental problems during waste management. This study extends previous work on RWW by analysing which pollution sources cause this contamination. Using existing data on the metal contents in various materials, and the amounts of these materials in RWW, the share of the elevated amounts of metals in RWW that these materials explain was quantified. Six different materials occurring in RWW were studied and the results show that they explain from 70% to 100% of the amounts of arsenic, chromium, lead, copper and zinc in RWW. The most important materials contributing to contamination of RWW are surface-treated wood, industrial preservative-treated wood, plastic and galvanised fastening systems. These findings enable the development and evaluation of strategies aiming to decrease pollution and resource loss from handling RWW. It is argued that source separation and measures taken further downstream from the generation site, such as treatment, need to be combined to substantially decrease the amount of heavy metals in RWW.

Abstract [en]

In Sweden recovered waste wood (RWW) is used for heat production, which reduces the share of waste that is landfilled and recovers the energy content of the waste. However, this waste contains contaminated materials that pollute RWW with heavy metals, causing downstream environmental problems. The main objective of this study was to analyse how different upstream-oriented strategies to manage RWW, influence the arising of environmental pressures downstream the waste management system. Today, the contaminated materials in RWW are handled together with the main waste flow. This upstream approach was compared with a separation strategy that removes contaminants from the main waste flow thereby handling these materials separately downstream the waste management system. An extended substance flow analysis (SFA) methodology that also includes resource issues was applied for the analysis. The results show that the upstream separation strategy exhibits potential environmental benefits. However, to accurately prevent environmental pollution also in a long time perspective, upstream separation strategies must be combined with downstream measures aimed to immobilise the contaminants in by-products. Otherwise, such separation strategies, as the current handling of RWW, may cause temporal and spatial shifting of problems. To enable immobilising measures, however, upstream separation strategies are important since they decrease the volume problem.

Abstract [en]

Wood preservatives contain hazardous substances that cause environmental implications during waste management. The objective of this study was to analyse the waste management of preservative-treated sawn timber in Sweden from a pollution perspective and in regard to the present waste policy. Firstly, the generation of waste was modelled and then the methods of disposal were analysed from direct inquiries to waste facilities and from mass balance considerations. The results show that the discarded amount of preservative-treated sawn timber has increased and today exceeds 150 000 tonnes per year. This waste generation will continue for many years and will contain several thousand tonnes of arsenic and chromium. According to the Swedish Waste Decree, preservative-treated sawn timber is to be separately handled as hazardous waste. At present, however, most of the waste unintentionally becomes dispersed in non-hazardous waste, making it difficult to control the outflows of hazardous substances from preservative-treated sawn timber.

Abstract [en]

In Sweden, large amounts of wood waste are generated annually from construction and demolition activities, but also from other discarded products such as packaging and furniture. A large share of this waste is today recovered and used for heat production. However, previous research has found that recovered wood waste (RWW) contains hazardous substances, which has significant implications for the environmental performance of recycling. Improved sorting is often suggested as a proper strategy to decrease such implications. In this study, we aim to analyse the impacts of waste regulation on the contamination of RWW. The occurrence of industrial preservative-treated wood, which contains several hazardous substances, was used as an indicator for contamination. First the management of RWW during 1995–2004 was studied through interviews with involved actors. We then determined the occurrence of industrial preservative-treated wood in RWW for that time period for each supplier (actor). From the results, it can be concluded that a substantially less contaminated RWW today relies on extensive source separation. The good news is that some actors, despite several obstacles for such upstream efforts, have already today proved capable of achieving relatively efficient separation. In most cases, however, the existing waste regulation has not succeeded in establishing strong enough incentives for less contaminated waste in general, nor for extensive source separation in particular. One important factor for this outcome is that the current market forces encourage involved actors to practice weak quality requirements and to rely on end-of-pipe solutions, rather than put pressure for improvements on upstream actors. Another important reason is that there is a lack of communication and oversight of existing waste regulations. Without such steering mechanisms, the inherent pressure from regulations becomes neutralized.